The fit of a garment to the body of the wearer is one of the key aspects of clothing design. Garment fit is critical for several reasons. First, garments that fit well are aesthetically pleasing to the wearer, as well as to others. Second, clothing that fits the body well does not hinder body movement. For instance, clothing that is too tight will prevent the body from undergoing its normal muscular expansions and contractions, causing discomfort to the wearer. Clothing that is too loose can hinder body motion by entangling the body in the garment or by adding unwanted bulk. Third, good fit often provides the function of garment securement. For instance, waist bands hold pants up, hat bands hold hats on, and some cuffs hold sleeves or pant legs in place. Fourth, there is a kind of fit that seals the environment beneath the clothing from leaking to the outer environment, or vice versa. This function is obvious in durable garments such as rainwear or cold weather clothing, and in disposable garments such as disposable diapers.
Elastics of many forms are often used to provide one or more types or garment fit. The forms of these elastics include composite materials such as those used in undergarment waist bands, and homogeneous elastomeric materials such as the waist and legbands found in many disposable diapers. There are also linear, and two-dimensional stretch elastics used in clothing. Waist bands, and elastic cuffs are considered linear, whereas in pantyhose the material stretches in two dimensions to provide a contoured body fit.
A common problem with elastics on factory manufactured articles, such as clothing, is that the amount of tension the elastic applies against the body is not right for each individual wearer. This problem arises because factory made clothing is manufactured in certain discrete sizes. While the elastic tension may be right for a person having dimensions in the middle of a particular size range, the tension may be too light for a slightly smaller person or too great for a somewhat larger person. If the tension is too light the garment may droop, while if too great, the elastics may leave red marks on the skin and cause discomfort.
Achieving garment fit using elastics also poses problems for the manufacturer of garments. First, attaching elastic materials to a garment, especially when the elastic is in a prestretched condition, requires somewhat complex material handling methods. Fixturing is often required to hold the elastic in a stretched condition, or the garment in a shirred or gathered condition while the attachment is made. This extra handling and fixturing can slow down automated production lines. Secondly, once the elastic is attached to the garment and tension is released, the garment shirrs in the area of the elastic making the garment unwieldy as it is passed either on to the next step in the manufacturing process or to a packing operation.
Prior to the development of the materials and method of the present invention, the problems associated with garment elastics have generally been dealt with in two basic ways. In particular, the problem of achieving the right amount of tension for the individual wearer has typically been accomplished by providing multiple fastening locations. These allow the elastic to be stretched different amounts as the garment is fastened to the body. A simple example of this is an elasticized belt for trousers that includes multiple fastening points at the belt buckle. This allows the wearer to select a wide range of waist band tensions. Another example of this is in disposable diapers having an elasticized waist band and tape fasteners. In this instance, the amount of tension in the waist band elastic can be controlled to some degree by the tension the mother applies to the waist band elastic before the tape fasteners are secured. While some degree of tension adjustment is afforded by this method, it is difficult for the person applying the diaper to precisely adjust this tension while the baby is squirming. This method of diaper elastic tensioning also compromises the position of tape attachment from the ideal. For instance, if the elastic is stretched to a great extent to achieve the desired tension, the tape fastening points may be far enough from their ideal location that the overall diaper fit becomes distorted. This distortion may cause poor fit in other critical areas, for example the leg band area.
The problem of assembling garment shirring elastic components which are not in tension when applied has typically been addressed in high speed manufacturing lines by the use of heat shrinkable elastics. These elastics are designed to be attached to a garment such as a disposable diaper while they are in the relaxed state or under low tension. After they are attached, heat is applied to the elastic at some point during or subsequent to the manufacturing process. Upon heating, these elastics contract and regain much of their original elasticity.
These heat shrinkable elastics are manufactured in several forms. Some are homogeneous materials. These are typically thermoplastic elastomers that were stretched to orient their molecular structures after casting. When they are heated after assembly in the diaper, they shrink back, losing some of their orientation. Other heat shrinkable elastics are composite structures such as those disclosed in U.S. Pat. No. 4,552,795 issued to Hansen et al. on Nov. 12, 1985. The structures disclosed by Hansen et al. are preferably comprised of prestretched elastomeric strands that are laminated between two relatively inelastic strips of film with inelastic thermoplastic polymer. Upon the application of heat the thermoplastic polymer softens, allowing the elastic member to move relative to the outer layers, thereby causing the outer layers and the article to which they are secured to elastically contract and shirr. Thus, if this laminate is attached to a portion of a garment, say a diaper waist band, the result upon heating is garment shirring in proportion to the relative movement between the elastic member and the outer layers of the laminate.
While solving many of the problems of elastic material factory assembly, the application of heat required to activate such prestretched and tensioned elastics may, in some circumstances, adversely affect other components in the article to be elasticized. Furthermore, such heat activatable materials do not help in a reasonable way in those situations where elastic adjustment by the consumer is desired. Heat activation by the consumer is impractical because it requires a heat source that is usually unavailable to the consumer, it is potentially dangerous, and it is difficult to reproducibly control without standardized processing conditions and equipment.
Accordingly, it is an object of the present invention to provide both elastic materials and methods of elastic application which avoid the foregoing problems altogether.
It is another object of the present invention to provide a premade elasticized garment including means to enable the person wearing or applying the garment to adjust the elastic tension of the garment to provide just the desired amount of elastic tension.
It is another object of the present invention to provide an elasticized garment including means for the consumer to set or adjust the tension in the garment without having to reposition the fasteners that hold the elastic in its stretched condition.
It is another object of the present invention to provide an article which can be applied to the wearer while it is not in tension and thereafter elasticized.
It is still another object of the present invention to provide method and apparatus for assembling a composite structure including a stretched elastic into an article while the composite structure is in a substantially untensioned condition and thereafter activating the elasticity in the article (either during manufacture or by the consumer) without damaging any of the other components comprising the article.